Yours appears to have a Hogue stock on it currently which has a longer length of pull than the Ruger wood carbine stock. You could try the wood factory carbine stock and see if that will fit him which is a similar length to what is on the Ruger 10/22. Another option is the Choate stock that has the AR-15 type collapsible stock that would allow the length of pull to be adjusted to fit but it does not fold.

If you are set on the strike force stock, I would upgrade it with the optional aluminum tube instead of the all plastic version.